The invention relates to a clamping fixture for detachably fixing a tool, in particular a disc. Clamping fixtures, in particular for disc-shaped tools are suitable particularly for portable power hand tools, and in this respect in particular for grinding hand power tools. A clamping fixture has been disclosed (German Patent Specification No. 3,012,836) in which one flange, which is arranged on the side of the tool pointing towards the housing of the power hand tool, is displaceable relative to the spindle and is coupled to the latter in such a way as to transmit torque. In this arrangement, this rear supporting flange is supported against axial displacement in an axial end position via a spindle shoulder forming a supporting element for the supporting flange. The other flange, which can be screwed onto the end of the spindle, consists of a nut having a separate clamping element which has a roughly hat-shaped cross-section and is supported axially against the flange of the clamping nut via a coil spring. When this clamping nut is screwed on and tightened, the pot-shaped clamping element is pressed axially against the tool via an axially compressed spring, and the tool is thereby tightened against the flange on the spindle side, the end face of a cylindrical extension of the clamping nut coming to bear directly on a facing axial side of the rear flange and, during further tightening of the clamping nut, this rear flange on the spindle side being tightened together with the clamping nut, if necessary until the rear flange comes to bear axially on the spindle shoulder surface forming the supporting element. In an angle grinder, the grinding disc is thereby supposed to be mounted with a predetermined contact pressure, and this contact pressure, is supposed to be ensured. This clamping fixture is also intended to enable a quick and simple exchange of the grinding disc and, at the same time, avoid overloading of the power hand tool, in particular the angle grinder. This is because, if the torque acting on the grinding disc is too great, the grinding disc stops, while the rear flange and also the clamping nut having the clamping member perform a relative movement thereto. The effect of the clamping nut automatically tightening further in operation, which otherwise makes it considerably more difficult to loosen the clamping nut when changing the grinding disc, is counteracted with this clamping fixture. Nonetheless, loosening of the clamping nut is here only possible with the assistance of a special auxiliary tool, the spindle, depending on the design of the machine, having to be appropriately counterheld by a second auxiliary tool, e.g. a spanner.